1. Field
The described technology relates generally to a flexible organic light emitting diode display and a manufacturing method thereof, and more particularly, to a flexible organic light emitting diode display having a thin film encapsulation layer structure including a plurality of inorganic and organic layers.
2. Description of the Related Art
An organic light emitting diode (OLED) display includes organic light emitting diodes (OLEDs), each of which includes a hole injection electrode, an organic emission layer, and an electron injection electrode.
Each OLED emits light using (utilizing) energy generated when electrons and holes are combined to create exitons in the organic emission layer and the exitons fall from an exited state to a ground state.
When a substrate of an OLED display including OLEDs is formed of a flexible film (such as a polyimide or the like), the OLED display can be easily bendable and is advantageous in forming a slim structure.
When the flexible OLED display is bent, stress occurs, specifically, tensile stress occurs at its convex outer side and compressive stress occurs at its concave inner side, and a neutral plane NP at which no stress occurs is present in an intermediate region therebetween.
A picture abnormality does not occur in the OLED display when (e.g., only when) the OLEDs are positioned at (e.g., in) the neutral plane.
However, when the thickness of the organic light emitting diode display is increased by internal and external films such as a polarizing film and a passivation film attached to the organic light emitting diode display, the tensile stress and the compressive stress are increased such that the neutral plane becomes narrow, thereby making it difficult to position the organic light emitting element at the neutral plane.
Further, the OLED display has a structure in which composite materials are layered and thus asymmetry of strains occurs due to a difference between tensile stress and compressive stress that are applied to outer and inner sides of a bent portion. Accordingly, it is difficult to position the OLED at the neutral plane, thereby causing display defects.
In addition, when the OLED display is bent, a moisture permeation path may be created in a display area through cracks formed due to excessive stress. Also, deformation of organic and inorganic layers forming a thin film encapsulation layer may cause deformation of the display area or other defects.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the described technology and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.